The invention relates to a holding apparatus for the spinal column in accordance with the preamble of the independent patent claim.
Holding apparatuses of this kind are used in deformations of the human spinal column. The principle is that the holding apparatuses are secured at a plurality of vertebrae and are connected to one another by means of one or more bars, through which the spinal column is mechanically held in a desired position.
Scoliosis is for example such a deformation of the spinal column. A lateral bending of the spinal column, which can also be entailed with a torsion of the individual vertebrae, is designated as a scoliosis. A distinction is made in principle between a total or C-shaped scoliosis (curvature of the spinal column to one side without a counter-curvature), a compound or S-shaped scoliosis (curvature with counter-curvature) and a triple scoliosis (curvature with a compensatory counter-curvature in the cranial and the caudal direction). A compound or S-shaped scoliosis is for example schematically indicated in FIG. 1. The broken line indicates the S-shaped form of the spinal column WS.
In an operational correction of the spinal column holding apparatuses, which e.g. have a hook, are secured to the vertebrae. The hooks grip beneath or behind respectively the lamina of the respective vertebra and hook in there, but they can however also grip on at the pedicles or at the respective transverse process (spine of a vertebra). Typically a holding apparatus is first secured at one vertebra each at the two ends of the region of the deformation of the spinal column. The holding apparatuses have a mount for a bar at their end which faces away from the hook. The bar has a predetermined shape which causes the spinal column to have a desired course when the individual vertebrae are connected to the bar in the region of the deformation by means of a holding apparatus.
Holding apparatuses are then likewise secured at the vertebrae in the region of the deformation of the spinal column. After the securing of a holding apparatus of this kind at the respective vertebra in the region of the deformation, the holding apparatus together with the vertebra is drawn towards the bar until the mount of the holding apparatus then takes up the bar. Then the respective vertebra is located in its desired position. The holding apparatus must now be firmly connected to the bar, since the spinal column naturally attempts to arrive back into the position of the deformation. This is somewhat difficult for the operating surgeon to accomplish since he must on the one hand carry out a lateral movement toward the bar of the vertebra together with the holding apparatus which is secured thereto, and must on the other hand possibly also effect a movement of the vertebra with the holding apparatus in the dorsal or ventral direction, and finally also possibly a longitudinal displacement of the vertebra together with the holding apparatus along the bar (thus practically a displacement in the cranial or caudal direction). Once he has carried out this movement of the vertebra together with the holding apparatus which is secured thereto, he must on the one hand hold the vertebra in the desired position and on the other hand fix the holding apparatus to the bar at the same time. This is connected with the above described difficulties in the handling for the operating surgeon since of course the spinal column attempts to restore the original (deformed) state.
An object of the invention is thus to propose a holding apparatus which facilitates the handling for the operating surgeon during the securing of the holding apparatus at the bar.
This object is satisfied by a holding apparatus such as is characterized by the features of the independent patent claim. Particularly advantageous embodiments result from the subordinate patent claims and from the following description of the exemplary embodiments which are illustrated in the drawings respectively.
The holding apparatus in accordance with the invention has means for retaining the bar in the mount which are executed in such a manner and can be brought into connection with the holding apparatus in such a manner that they temporarily retain in the mount a bar which is introduced into the mount until the holding apparatus is fixed to the bar with the help of the means for producing the rigid connection. This means that the operating surgeon can achieve a temporary fixing of the holding apparatus and thus of the corresponding vertebra in a simple manner although the spinal column attempts to restore the state of the deformation. Nevertheless the holding apparatus remains displaceable on the bar in the axial direction of the latter.
The operating surgeon can thus first bring a vertebra from a region in which a deformation of the spinal column is present into the desired position and then connect the holding apparatus rigidly to the bar so that at first a vertebra or the holding apparatus which is connected thereto respectively is rigidly connected to the bar. Alternatively, the operating surgeon can also first temporarily secure a plurality of vertebrae from the region in which the deformation of the spinal column is present to the bar so that the former are still displaceable in the axial direction on the bar and only then determine the final position of the respective vertebra. This has the advantage that the holding apparatuses and the vertebra which are secured thereto are still xe2x80x9clongitudinally displaceablexe2x80x9d relative to one another so that the final position of the holding apparatuses and the vertebrae which are secured thereto need be determined only after the correction of an entire region of the spinal column. This then takes place in the same way through the rigid connection of the holding apparatus to the bar.
The mount for the bar is advantageously designed in such a manner that the means for retaining the bar can be brought into connection with the mount itself. This region, that is, the mount itself, is still the best accessible for the surgeon during the operation after the securing of the holding apparatus at the vertebra (e.g. by means of a hook or a pedicle screw).
Furthermore, the means for retaining the bar can advantageously be designed in such a manner that they receive a clamping screw which form the means for producing the rigid connection of the holding apparatus to the bar. This kind of rigid fixing of the holding apparatus to the bar can be realized simply and without a great effort and results in a reliable connection of the holding apparatus to the bar.
The mount for the bar and the means for producing the rigid connection of the holding apparatus to the bar can preferably be executed in such a manner that they form a three point support. This kind of support is well defined and particularly reliable.
For the temporary fixing, a plurality of variants advantageously present themselves. One variant provides for example that the means for retaining the bar comprise an element which enters into a snap connection with the holding apparatus or with the bar.
Another variant provides that the means for retaining the bar comprise a cover which is executed in such a manner that it enters into a connection of the manner of a bayonet lock with corresponding means at the holding apparatus.
Yet another variant provides that the means for retaining the bar comprise a cover which can be pushed onto the mount in the axial direction and which has a through-going threaded bore through which a clamping screw can be screwed through completely; and that the mount is designed to be elastically deformable in that end region of its wall which faces the cover. There the wall has projections which is in engagement after a deformation with projections which are correspondingly formed at the cover. The bar is snapped in in the mount in this variant so that it can not inadvertently escape.
Still another variant provides that the means for retaining the bar comprise a sickle shaped finger which is pivotally arranged in a cut-out between two stationary fingers which are formed in the manner of a hook at the mount. At the respective surface of the stationary hook-like finger pointing to the movable finger, a pin which points to the movable finger is in each case provided. This pin engages into a corresponding cut-out which is provided at the movable finger in the respective surface which points to the stationary finger. In this the movable finger has an extension which projects outwardly beyond the cut-out and which is provided with a thread onto which a nut can be screwed. Thus through pivoting the finger the bar can at first be temporarily retained in the mount. Then the final rigid connection of the holding apparatus to the bar can be effected through a tightening of the nut.
Further particularly advantageous embodiments result from the description of the following exemplary embodiments of a holding apparatus in accordance with the invention. Shown, partly in schematic illustration and/or in section, are: